This invention relates to improved sulfonated aromatic condensate (SAC) compositions to enhance the stain resistance of carpet fibers. SAC's used to impart stain resistance are generally synthesized by the condensation of formaldehyde with diphenolsulfone and phenolsulfonic acid (Blyth and Ucci, U.S. Pat. No. 4,592,940). The functionality and reactivities of the monomers are such that a complex mixture containing random sequences is obtained. The presence of the diphenolsulfone promotes cross-linking of the polymer backbones and high molecular weights or sizes.
The SAC's are most effective for promoting stain resistance when concentrated near the fiber surface or "ring-dyed". Therefore, it is necessary to carefully select the type of SAC mixture and tailor its characteristics to the requirements of the fiber morphology and application methods. If not properly designed, the SAC will not impart the desired stain resistant properties at extremes of significant application variable ranges.
The preferred method for application of the SAC stain resist chemistry is by an "aftertreatment", after the carpet is already dyed. The aftertreatment may be either a batch or continuous process. The most commercially significant aftertreatment process involves continuous application of the treatment liquor using a specially designed applicator, such as the Kuster Flex-nip or Otting Thermal Chem, which is then followed by a dwell period at elevated temperature using a short vertical steamer. In this application process, the steaming time has a significant effect on the stain resistance, depending on the SAC. The typical steamer length is approximately 80 linear ft., but can vary. Typical practical limits on steaming time are generally between 0.5 and 4 minutes, i.e., carpet running speed of 20 to 160 ft./min.
Size Exclusion Chromatography (hereinafter SEC) is a well known analytical technique to determine molecular size and is also known as aqueous gel permeation chromatography, as described in pages 81-84 of A Guide to Materials Characterization and Chemical Analysis, Edited by John P. Sibilia, published by VCH 1988. Molecular size is measured by hydrodynamic volume defined by elution volume (Ve), sometimes also called retention volume. It is the volume of the material eluted at a certain elution time through the gel permeation apparatus as shown by the chromatography curve, e.g. the area under the peak of the chromatography curve generated while eluting the sample. More specifically, Ve is the peak elution or retention time (on the chromatograph) multiplied by the flow rate of the mobile phase. See Chpt. 10 of Modern Size Exclusion Liquid Chromatography by Yau et al., Whiley-Interscience 1979, page 94 of Thin-Layer Chromatography by Bolliger et al., Springer-Verlag 1965 and pages 336 to 357, particularly 337 (and page 377) of the Seminar Proceedings of 6th Int' l Seminar on Gel Permeation Chromatography, Waters, 1968.